Biology - Semester 2 - Final Exam

The picture of the double-helix model of the DNA molecule resembles a twisted ladder. What makes up the rungs (steps) of the twisted ladder?

• paired phosphate groups
• paired nitrogenous bases
• paired sugars
• hydrogen and oxygen atoms

Which of the following events occurs in DNA replication in prokaryotes?

• Regulatory proteins bind to all of the nucleotides on the DNA molecule.
• Enzymes “unzip” the DNA molecule by breaking ionic bonds between base pairs.
• Replication starts from a single point and proceeds in two directions until the entire chromosome is copied.
• Replication starts from multiple points and proceeds in two directions until the entire chromosome is copied.

After examining the DNA of different organisms, which of the following did Erwin Chargaff conclude about the four bases?

• A = T and C = G
• A = C = G = T
• A = C and G = T
• A + T = C + G

Combining the work of other scientists with their own research, Watson and Crick discovered that two strands of DNA join together to form a(n)

• nucleotide.
• X in a circle.
• double helix.
• covalent bond.

What holds base pairs together?

• hydrogen bonds
• sugar-phosphate backbones
• pairs of double-ringed nucleotides
• nitrogen-carbon bonds

The process that makes an exact copy of a cell's DNA is called

• conservation.
• preservation.
• replication.
• synthesis.

Which of the following phrases best describes the function of meiosis?

• reduces chromosome number by half, produces gametes
• reduces chromosome number by half, produces diploid cells
• conserves chromosome number, produces haploid cells
• conserves chromosome number, produces genetically identical cells

If females are XX, Males are _____

• YY
• XX
• XY

Which is the term for the group of proteins that organizes and condenses long strands of DNA into tight coils?

• telomeres
• centromeres
• chromatids
• histones

What is the main difference between binary fission and mitosis?

• There is no DNA replication in binary fission.
• Two parents are required for mitotic reproduction.
• Binary fission occurs in single-celled organisms only.
• Mitosis takes place only in sexual reproduction.